Examining the interlayer interactions formed between reduced graphene oxide and ionic liquids
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esearch Letters
Examining the interlayer interactions formed between reduced graphene oxide and ionic liquids Natis Shafiq and Muge Acik, Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080-3021 Daniel R. Dreyer, Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712 Juan Juarez, Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080-3021 Christopher W. Bielawski, Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712 Yves J. Chabal, Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080-3021 Address all correspondence to Yves J. Chabal at [email protected] (Received 15 February 2013; accepted 18 February 2013)
Abstract It is important to understand the electrolyte–electrode interactions for fabricating graphene oxide (GO)- and ionic liquid (IL)-based ultracapacitors. Therefore, we explored how the type and size of the cations in various ILs determine the nature of processed materials. In all cases, the ILs intercalate into the graphitic structure but marked differences are observed during exfoliation via thermal reduction. The combination of a long alkyl chain ammonium-based cation and a large-volume anion leads to strong interactions and defect formation, as evidenced by CO2 production during annealing. In contrast, using the same anions but different cations stabilize the GO functional groups below 400 °C.
Substantial improvement in the cycling efficiency of energy storage devices is necessary to increase their overall performance, requiring a focused effort in the development of new nanoscale materials. Recently, ultracapacitors have attracted attention because, in contrast to batteries, they exhibit high
power delivery (10 kW/kg) and a long life cycle.[1] Ultracapacitors typically consist of two porous carbon electrodes separated by an ion porous polymer membrane. When a supporting electrolyte is added, an ionic current can flow between the electrodes.[2] The performance of ultracapacitors
Figure 1. (a) Chemical structures of the ILs studied: IL-1 (N-methyl-N-octylpyrrolidinium bis(trifluoromethanesulfonyl)imide), IL-2 (N-octyl-N,N, N-tributylammonium bis(trifluoromethanesulfonyl)imide), IL-3 (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), IL-4 (N-octyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide) and (b) infrared transmission absorbance spectra of GO and GO–IL composites in 2:1 ratios (w/w) prepared in deionized water at room temperature: GO–IL-1, GO–IL-2, GO–IL-3, and GO–IL-4.
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can be improved by using new kinds of electrode materials and electrolytes, such as graphene-based nanomaterials, that possess high intrinsic surface areas and are chemically inert under a wide range of applied potentials.[1] Moreover, the energy density of ultracapacitors increases at higher cell vol
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